The advantages of defogging and de-icing the windows of a vehicle have long been recognized for purposes of improving vehicle safety during inclement weather. However, unfortunately many systems used today to defog and de-ice windows of the vehicle, particularly side windows, require the vehicle's engine to first achieve a sufficient operating temperature. More specifically, many known systems used today to heat side windows employ a defrosting vent positioned adjacent a forward portion of the side window. This defrosting vent provides warm air blowing across the interior face of the side window to heat the side window. However, these systems are very inefficient when considering the time necessary to achieve sufficient heat. The warm air is a product of the vehicle's heating system, which only operates once the vehicle engine has achieved at least a minimum operating temperature. As many drivers know, modern automobile engines may require an extended amount of time to achieve this minimum operating temperature. Accordingly, attempts have been made to provide a means of directly heating side windows of a vehicle which results in applying immediate and direct heat to the window surface when desired.
U.S. Pat. No. 5,466,911, issued to Spagnoli et al., discloses an electrically heated window assembly by producing a concentration of heat at the portion of the front window through which a driver views an exterior mirror. This concentration of heat is produced by providing a pair of bus bars, positioned on opposing ends of the window, and a transparent conductive film positioned between the pair of bus bars. During operation, electricity flows from one bus bar to the other bus bar through the transparent conductive film, thereby producing heat within the film to heat the window.
However, the Spagnoli et al. system suffers from a number of significant disadvantages. By way of non-limiting example, the transparent conductive film is particularly susceptible to damage as it extends across the entire interior surface of the window. Such damage may include scrapes and/or gouges along the surface, peeling of the conductive film, or even failure of particular heating sections due to severing of the conductive film. Moreover, the Spagnoli et al. system may not minimize manufacturing costs as it includes a complicated, multi-part configuration requiring the application of bus bars, transparent conductive film, non-conductive breaks, temperature sensors, and the like.
U.S. Pat. No. 4,410,843, issued to Sauer et al., discloses an electrically controlled sliding window and proximity detector which includes a window heating system. The Sauer et al. system uses heat generated by current flowing through a series of horizontal, parallel conductors positioned generally in the upper half of the window. The series of conductors electrically interconnect a pair of bus bars, which extend along the forward and rearward edges of the window glass within view of the operator. During operation, current flows from a current source from one bus bar to the other bus bar through the conductors, which generate heat to heat the upper portion of the side window.
However, the Sauer et al. system suffers from a number of significant disadvantages. For example, the Sauer et al. system fails to directly heat the portion of the side window through which the operator views the exterior side view mirror. The Sauer et al. system heats the top portion of the side window, yet does not heat the portion of the side window adjacent the side view mirror. In fact, the lowest portion of the heated region of the Sauer et al. system generates the least amount of heat due to the increased length of the conductor relative to the other conductors. This increase length of the conductor produces a higher resistance in the conductor wire, thereby limiting current flow relative to the shorter conductors. Accordingly, in operation, the Sauer et al. system will first defog and/or de-ice the top of the side window and, thus, the operator must still wait for sufficient heat to build up to defog and/or de-ice the lower section of the heated region.
Accordingly, there exists a need in the relevant art to provide a side window glass having a heated region positioned generally within a line of sight of side view mirror. Furthermore, there exists a need in the relevant art to provide a heated side window glass that is simple in design and provides concentrated direct heating solely at the line of sight region of the glass. Still further, there exists a need in the relevant art to provide a heated side window glass that does not suffer from the disadvantages of the prior art.